1. Field of the Invention
The present invention relates to expansion pipe joints for extendibly and contractibly connecting pipes, and more particularly to an expansion pipe joint including an inner sleeve axially slidably mounted in an outer sleeve and retained against detachment from the outer sleeve.
2. Description of the Related Art
Expansion pipe joints as noted above include a flexible expansion pipe joint. Conventionally, a flexible expansion pipe joint has a retainer ring fixed to an outer surface of the inner sleeve, and fitted in a broad annular groove formed on an inner surface of the outer sleeve. The inner sleeve is retained in place inside the outer sleeve by contact between the ring and an inside wall of the annular groove (see Japanese Utility Model Publication Kokai No. 1981-23786, for example).
This pipe joint has the disadvantage of requiring great trouble in attaching the ring in that the ring is fixed to the outer surface of the inner sleeve to retain the inner sleeve in place. Particularly where the ring is inserted into and fixed to an annular groove formed on the outer surface of the inner sleeve, the inner sleeve has a wall thickness partly reduced for the annular groove, resulting in a disadvantage in terms of strength.